This invention deals generally with a sediment filter for stormwater and more specifically with a permeable filter cloth bag sewn to form layers of parallel tubes of filter cloth that give each layer the pleated look of a typical air mattress.
Stormwater bag-type filters within enclosures are quite useful because they facilitate the trapping and disposal of contaminants and sediment in runoff from streets, parking lots, and other surfaces. In such an arrangement, the full filter bag can be removed from its enclosure, replaced by a fresh filter bag, and the full filter with its trapped material can be disposed of properly. However, a major problem with bag-type stormwater filters is the tendency of the top cloth surfaces of such filter bags to float upon the accumulation of water within the bag and raise these surfaces to virtually the same level as the water level in the flowing stream. This results in insufficient water pressure to move liquid through the filter and can also cause premature bypassing of the filter bag through the typical bypass structure, thus completely negating the filter action. Another problem with bag-type filters is the large “footprint” required for the enclosure relative to the amount of active filter area. The typical bag-type filter requires a footprint of approximately one-half the active filter area, which requires large structures for the enclosures. It would be very beneficial to have bag-type stormwater filters that operated consistently and included large active surface areas within smaller enclosures.